Advances in technology and the increasing pressures of congested road environments have encouraged the development and adoption of Personal Navigation Devices (PND). The abbreviation PND is sometimes used to refer to a “portable navigation device”, but in this specification will be given its more expansive definition, covering any kind of personal navigation device that is either portable (e.g., can be fixed to an auto windscreen using a suction mount), or embedded (e.g. permanently fixed into an automobile). PNDs can be dedicated navigation devices (e.g., a device whose primary function is navigation) or can have multiple other applications (e.g., media players) or can have a primary function other than navigation (e.g., a mobile telephone). PNDs are used predominantly, but not exclusively, in cars and other motor vehicles. PNDs incorporate geographical map databases including road information and points of interest. They generally include software which allows the user to input a destination and to be provided with one or more routes; driving instructions are issued to guide the driver along the selected route to the destination. The PND may include a mount attachable to an automotive windscreen.
The selection of the route along which to guide the driver can be very sophisticated, and the selected route may take into account existing and predicted traffic and road conditions, historical information about road speeds, and the driver's own preferences for the factors determining road choice. In addition, the device may continually monitor road and traffic conditions, and offer to or choose to change the route over which the remainder of the journey is to be made due to changed conditions.
Road travel is a major part of everyday life for businesses, for other organizations, and for private individuals. The costs of traffic delays can be very large. The purely financial cost has been estimated as billions of pounds in the UK alone. In view of these costs, systems which can assist drivers to optimize their travel, for instance by selecting the best route and by avoiding congestion delays, are of significant value. In fact, a diverse array of driver information systems has grown up. The longest established are broadcast radio traffic reports which aggregate data from a number of sources such as the police, eye-in-the-sky, and more recently mobile phone calls from drivers stuck in traffic jams, to provide subjective advice about incidents and delays. Radio Data System (RDS) radios make these systems more effective by automatically cutting to traffic reports from normal radio programs. Static route planning systems are provided on the websites of major motoring organizations such as the Automobile Association (AA) and RAC in the UK. These allow a driver to enter the points of a journey and to be given a route and driving instructions for that route.
In the recent past, in-vehicle personal navigation devices have been introduced based on Global Positioning System (GPS) technology. Examples of these are the TomTom GO™ series of PNDs. Personal navigation devices use the GPS system to discover the exact position of the vehicle on the road network and to plot the location of the vehicle on an on-screen road map. PNDs contain a mechanism for computing best or good routes between two or more points on the road network and can direct the driver along the chosen route, continually monitoring their position on that route. Personal navigation devices have begun to incorporate traffic information into their services, and in some, traffic information is integrated into the route selection process: the PND will route around congested roads. Where traffic information is provided by the PND, the user can observe delays where they impact the selected route, and guide the device to re-plan a route avoiding the delayed sections of road if they consider this necessary. Real-time traffic monitoring systems, based on various technologies (e.g. mobile phone calls, fixed cameras, GPS fleet tracking) are being used to identify traffic delays and to feed the information into notification systems.
As mentioned above, road traffic can be monitored in real-time on the basis of mobile phone calls as follows. In a mobile phone system, subscribers carry handsets. When the subscriber initiates or receives a call or text message or data session, radio communication takes place between the handset and a base transceiver station (BTS), the familiar mast on the modern landscape. As well as transmitting an encoding of the message passing between caller and call recipient, the handset and BTS transmit a large amount of control information between themselves for the purposes of reliably and efficiently supporting the communication; for example the system must choose when to pass the call to another BTS as the subscriber moves about. The control information in a Global System for Mobile Communications (GSM) system or in a Universal Mobile Telecommunications System (UMTS), contains information on the signal strength of neighboring BTSes, timing advance information to instruct handsets further from the BTS to transmit earlier in order to match their time slot, transmission error rates and much more. Other technologies, such as code division multiple access (CDMA), use different information to achieve the same purposes of reliable and efficient communication. Collectively, these parameters are being referred to as the mobile phone control parameters. A location parameter database (LPDB) correlates mobile phone control parameters with geographical locations of handsets. LPDBs can be constructed and maintained by one of several means, and can map one of several useful subsets of control parameters to geographical locations.
For more background information on such PNDs and above services, see, e.g., US patent application publications US 20070225902; US 20070185648; US 20070118281; and US 20070117572, all owned by TomTom International B.V. and herein incorporated by reference.
For more background information on monitoring road traffic through monitoring usage of mobile telecommunication devices onboard road vehicles see, e.g., WO200245046 (“Traffic monitoring system”); and WO2007017691 (“Method of finding a physical location of mobile telephone at a given time”), incorporated herein by reference.